1. Field of the Invention
The present invention relates to a hatch cover for hopper cars and a method of making the same.
2. Information Disclosure Statement
In general, hopper cars are used primarily to transport commodities which are perishable or require protection from contamination and the weather, or to provide a method of transporting materials that may be hazardous to the environment. Hopper cars are used in the chemical and petrochemical industries to transport chemicals, in the farming industry to transport grain, and in other industries to transport bulk materials such as cement. Hopper cars are characterized, because of the types of materials that are carried in them, by the fact that materials are loaded into the top of the car instead of through doors on the side, as was the case, for example, in box cars. It has been found to be most convenient to provide hatches in the top of hopper cars for loading the transported materials. To provide the kind of integrity needed to transport the types of materials listed above, hatch covers must be provided which are strong and provide a good hatch seal.
Although a number of hatch configurations are known in the art, hatches for hopper cars are generally round in shape as is illustrated in, for example, "The Car and Locomotive Cyclopedia", 4th edition, Simmons-Boardman, 1980. In the prior art, hatch covers have generally been made of cast aluminum, steel, or fiberglass, but these materials have certain disadvantages. Hatch covers of cast aluminum are expensive to make and are brittle, and are therefore easily broken. Hatch covers made of steel are expensive to make, are heavy, and unless they are made of the more expensive stainless steel, they are subject to rusting and to the corrosive action of chemicals that may be transported in the hopper cars. Fiberglass covers are extremely light weight and flexible, making it difficult to maintain a suitable seal between the hatch cover and the hatch.
Hatch covers, particularly round hatch covers, are made with a variety of known sealing mechanisms. For example, round hatch covers may be sealed using the Mon-O-Wheel hatch as is illustrated at page 180 of the "Car and Locomotive Cyclopedia". Also known in the art, as is illustrated at page 188 of the "Car and Locomotive Cyclopedia" are hatch covers having a locking arm traversing the diameter thereof. When hatch covers having a locking arm are made of steel, the covers are heavy and are labor intensive to produce, since the locking arm must be riveted to the lid. When such hatch covers are made of fiberglass, although a good seal can be obtained at the two ends of the locking arm, a strong seal cannot be obtained at the edges of the hatch remote from the locking arm because of the flexibility of the fiberglass.
U.S. Pat. No. 4,126,094, issued to Zimmerle et al on Nov. 21, 1978, also shows a hatch cover and holding bar of conventional design.
Applicant has also filed, as sole or co-inventor, the following applications relating to hatch covers and hold-down bars:
Ser. No. 412,416, filed 08/27/82 PA1 Ser. No. 456,154, filed 01/06/83 PA1 Ser. No. 459,067, filed 01/19/83 PA1 Ser. No. 459,069, filed 01/19/83 PA1 Ser. No. 459,273, filed 01/19/83 PA1 Ser. No. 462,730, filed 01/31/83
Accordingly, there is a need in the art for a hatch cover which is easy and inexpensive to build, is relatively light in weight, has sufficient rigidity to provide uniform pressure around the perimeter thereof when locked in the closed position to provide a good seal, is resistant to corrosion, and is not labor intensive to build.
Reaction injection molding is known in the art as is illustrated by "Plastics Technology", pages 33-44, March 1983. In reaction injection molding, at least two materials which react to each other to form a polymer are separately, and simultaneously, injected into a mold of the desired shape, said chemicals being mixed as they are injected into the mold. Since the chemicals that create the polymer react chemically with one another on contact, a curing step is not required to produce a stable polymeric material. The reactive chemicals used to make the polymer must be chosen so that the final polymeric material has the properties desired. Typically, no releasing agents are required since heat is not required for a cure, and the polymer produced by the technique, in most cases, can easily be removed from the mold.